This invention is directed in general to electrophotographic reproduction apparatus, and more particularly to a self-coiling exposure shade for preventing unwanted illumination of the photoconductive member of an electrophotographic reproduction apparatus.
Electrostatographic reproduction apparatus, and particularly electrophotographic apparatus, typically reproduce information by exposing a uniformly charged dielectric member to an image of information. For example, a light image of information to be reproduced modifies the uniform charge on the photoconductive surface of a dielectric member so as to form a charge pattern, or latent image, on the surface corresponding in an image-wise configuration to the information to be reproduced. Pigmented marking particles, exhibiting a charge of opposite polarity to that of the latent image charge pattern, are brought into contact with the photoconductive surface and adhere to the areas of the surface where the charge pattern exists to develop the latent image and form a transferable image. Thereafter, the transferable image is transferred to a receiver member and permanently fixed to such member by heat and/or pressure to form the desired reproduction.
One method for exposing the photoconductive surface involves forming a light image of a document by directing light from a lamp assembly at a document. The light reflected from (or transmitted through) the document is directed through a lens unit into focus on the photoconductive surface. The light from the lamp assembly may illuminate the entire document at one time (referred to as flash exposure), or may be passed through a slit and moved relative to the document to illuminate successive line segments of the document (referred to as scan exposure).
When a document is scan exposed by moving the lens unit beneath a stationary document-supporting platen, only light directed through the lens unit should expose the photoconductive surface. That is, unwanted illumination must be prevented from reaching the photoconductive surface in order to prevent undesirable artifacts from being formed in the reproduction. Examples of typical prior art shades for preventing unwanted illumination of the photoconductive surface are shown in U.S. Pat. Nos. 3,677,633 (issued July, 18, 1972, in the name of Huber); 3,807,856 (issued Apr. 30, 1974, in the name of Rodriguez); and 4,050,812 (issued Sept. 27, 1977, in the name of Koizumi et al). The shades of the 3,677,633 and 4,050,812 patents are of the roll-up curtain type and require spring mechanisms to effect such roll up action. Such spring mechanisms add to the complexity and cost of the associated reproduction apparatus. The 3,807,856 patent employs a collapsing bellows as the exposure shade. While no spring mechanism is required for moving the bellows with the lens unit, the use of a bellows necessitates a substantial area in which to accommodate the bellows. This increases the size of the exposure portion of the associated reproduction apparatus.